public/constants

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      <h2><a href="./">Go by Example</a>: Constants</h2>
      
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            <p>Go supports <em>constants</em> of character, string, boolean,
and numeric values.</p>

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            <a href="https://go.dev/play/p/Vw-pXSfo9_b"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
          <pre class="chroma"><code><span class="line"><span class="cl"><span class="kn">package</span> <span class="nx">main</span></span></span></code></pre>
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          <pre class="chroma"><code><span class="line"><span class="cl"><span class="kn">import</span> <span class="p">(</span>
</span></span><span class="line"><span class="cl">    <span class="s">&#34;fmt&#34;</span>
</span></span><span class="line"><span class="cl">    <span class="s">&#34;math&#34;</span>
</span></span><span class="line"><span class="cl"><span class="p">)</span></span></span></code></pre>
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            <p><code>const</code> declares a constant value.</p>

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          <pre class="chroma"><code><span class="line"><span class="cl"><span class="kd">const</span> <span class="nx">s</span> <span class="kt">string</span> <span class="p">=</span> <span class="s">&#34;constant&#34;</span></span></span></code></pre>
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          <pre class="chroma"><code><span class="line"><span class="cl"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
</span></span><span class="line"><span class="cl">    <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">s</span><span class="p">)</span></span></span></code></pre>
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            <p>A <code>const</code> statement can appear anywhere a <code>var</code>
statement can.</p>

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          <pre class="chroma"><code><span class="line"><span class="cl">    <span class="kd">const</span> <span class="nx">n</span> <span class="p">=</span> <span class="mi">500000000</span></span></span></code></pre>
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            <p>Constant expressions perform arithmetic with
arbitrary precision.</p>

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          <pre class="chroma"><code><span class="line"><span class="cl">    <span class="kd">const</span> <span class="nx">d</span> <span class="p">=</span> <span class="mf">3e20</span> <span class="o">/</span> <span class="nx">n</span>
</span></span><span class="line"><span class="cl">    <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">d</span><span class="p">)</span></span></span></code></pre>
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            <p>A numeric constant has no type until it&rsquo;s given
one, such as by an explicit conversion.</p>

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          <pre class="chroma"><code><span class="line"><span class="cl">    <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nb">int64</span><span class="p">(</span><span class="nx">d</span><span class="p">))</span></span></span></code></pre>
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            <p>A number can be given a type by using it in a
context that requires one, such as a variable
assignment or function call. For example, here
<code>math.Sin</code> expects a <code>float64</code>.</p>

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          <pre class="chroma"><code><span class="line"><span class="cl">    <span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">math</span><span class="p">.</span><span class="nf">Sin</span><span class="p">(</span><span class="nx">n</span><span class="p">))</span>
</span></span><span class="line"><span class="cl"><span class="p">}</span></span></span></code></pre>
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          <pre class="chroma"><code><span class="line"><span class="cl"><span class="gp">$</span> go run constant.go 
</span></span><span class="line"><span class="cl"><span class="go">constant
</span></span></span><span class="line"><span class="cl"><span class="go">6e+11
</span></span></span><span class="line"><span class="cl"><span class="go">600000000000
</span></span></span><span class="line"><span class="cl"><span class="go">-0.28470407323754404</span></span></span></code></pre>
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        Next example: <a href="for">For</a>.
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      by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> and <a href="https://eli.thegreenplace.net">Eli Bendersky</a> | <a href="https://github.com/mmcgrana/gobyexample">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
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